Automated chemical analyzers, such as clinical chemical analyzers, perform tests by combining reagents with samples. Analyzers hold reagents in reagent containers on board the analyzer for transfer by pipetting. Analyzers may present reagent containers at a pipetting location in rapid succession to achieve high test throughput. This rapid presentation can cause reagents in large reagent containers to slosh. Reagent sloshing may cause a variety of problems including pipetting errors, level sensing errors, and pipette contamination.
Reagent containers are rarely completely full. Even freshly opened containers usually have an unfilled headspace into which reagents can move. As an analyzer uses reagents the amount of headspace increases. This unfilled volume allows reagents to shift position within reagent containers in response to applied forces.
Moving reagent containers applies forces to reagents inside. For example, when an analyzer presents reagent containers on a rotating turntable, the reagents in the containers are subject to a variety of inertial forces. These forces include centrifugal force that accelerates the reagents radially outwardly, Coriolis force that accelerates particles of fluid perpendicularly to their velocity, and angular acceleration and deceleration that accelerate reagents in the reverse of the direction of the turntable acceleration. Reagents move within reagent containers in response to these forces. This motion is manifested as waves with amplitude, spectrum, and duration dependent on reagent container geometry, on fill level, on speed of motion and acceleration, and on reagent fluid parameters. Reagent waves slosh through the reagent container, altering the local height of reagent even after motion stops.
Prior reagent containers include a variety of pipes and baffles to reduce the effect of reagent sloshing, but these suffer from shortcomings including inadequate slosh protection, bubble and aerosol formation, high dead volume, blocking of openings with reagent films, and limitations on bottle fill rate. Some art includes a vertical pipe that takes up the entire opening of a blow-molded bottle and includes a ventilation hole within the vertical pipe wall (see FIG. 1 PRIOR ART). Such ventilation holes are susceptible to blocking by a liquid film of surfactant-containing reagents. The external surfaces of blow-molded bottles of the prior art are controlled by contact of an expanding parison with the walls of a mold cavity. The internal surfaces are not dimensionally controlled; they result from flow patterns of softened polymer in contact with colder metal of the mold cavity. Parting lines resulting from intrusion of polymer material between parting surfaces of a moldbase during molding may produce sink marks or other deformations on the inner surface of bottle overlaying the parting line. Parting lines may commonly occur along a midline of the bottle, which is a preferred location for fluid transfer operations. Consequently, the internal surfaces of blow-molded bottles are of varying thickness and surface finish. The walls are not sufficiently smooth and flat for consistent attachment of a pipe at a fixed position, particularly if that position overlays parting lines or other mold geometry. Other art includes pipes with flow resistance elements near the bottom that retard fluid transfer in response to transient forces. Such flow resistance elements increase inaccessible dead volume in the reagent container. There is therefore a need to provide a reagent container not subject to these shortcomings.